Reactions on polymer Surfaces by using an excimer laser, which emits high-intensity pulsed light in the ultraviolet region, are being studied vigorously for fine-surface treatment and fine-surface processing of polymers, aimed at both acquiring basic knowledge and applying such reactions practically.
The present inventors have reported that, by irradiation with a laser beam, (1) a fine structure was formed on the surface of a polymer, which surface can be applied to a liquid crystal alignment film [H. Niino, A. Yabe, et al. Japan Journal of Applied Physics, Vol. 28, p. L2225 (1989); Applied Physics Letters, Vol. 55, p. 510 (1989); ibid, Vol. 54, p. 2159 (1989); ibid, Vol. 57, p. 2368 (1990); and Journal of Photochemistry, Photobiology A: Chemistry, Vol. 65, p. 303 (1992)], and (2) an irradiation-positionally selective electroless plating could be conducted by using a change in surface potential [H. Niino, A. Yabe, et al., Applied Physics Letters, Vol. 60, p. 2697 (1992)]. These are based upon the formation of ion species or a periodic change in surface shape.
W. G. Hawkins et al. [W. G. Hawkins and P. L. Houston, Journal of Physical Chemistry, Vol. 86, p. 704 (1982)] attempted photochemical decomposition of hydrazine (N.sub.2 H.sub.4) in a gaseous phase with irradiation with an ArF excimer laser beam (wavelength: 193 nm), and detected radical species, such as NH.sub.2 and N.sub.2 H.sub.3, and nitrene species, such as NH, as formed intermediates, spectroscopically. Thus, photochemical decomposition reaction of gaseous molecules by using an ultraviolet laser can generate intermediates having high chemical reactivity with high efficiency. However, Hawkins et al. did not at all suggest industrial usefulness and applicable measures regarding the surface-treatment method that uses these intermediates.
On the other hand, fluorocarbonpolymers, typically poly(tetrafluoroethylene), are thermally and chemically highly stable and therefore draw wide industrial interest. However, since fluorocarbonpolymers are very low in surface free energy, their surface exhibits both water repellency and oil repellency, and the adhesion of the surface is poor. As a result, their field of the application is limited in practice. Accordingly, in order to improve the adhesion of their surface keeping the properties of the molded article itself unchanged, introduction of polar groups by various surface-modification processes is being studied. For example, there are reported a method that uses plasma treatment [M. Morra et al., Langmuir, Vol. 5, p. 872 (1989)], a chemical activation method that uses a solution of an alkali metal [E. R. Nelson et al., Industrial and Engineering Chemistry, Vol. 50, p 329 (1958)], and a laser irradiation method that uses a boron/aluminum/ammonia compound (Toyoda and Murahara, Japanese Patent Application (OPI) No. 196834/1990). These methods are attended with such problems as that the polymer surface is physically damaged; it is difficult to modify the surface locally; and sufficient care must be taken in handling the reagents. Further, these reports did not at all suggest depositing a metal film on the surface that have been irradiated with a laser beam.